Study On Stress And Thermal Conductivity Of Silicon Oxide Waveguide Optical Switch

Planar Lightwave Circuits（PLC）technology based on silicon-based optical waveguides,due to its advancements in mass production of wafers,is driving the applications of functional components to meet the industrial growth.In this work,we study the film stress characteristics and thermal conductivity characteristics of Mach-Zehnder Interferometer（MZI）type 2x2 thermo-optic switches in PLC technology and their influences on the device optical performance.First,we carry out the numerical simulations for all the interactions between the film layers with the theoretical models and then find a nonlinearly distributed structural stress on a 6-inch silicon wafer,an additional stress to the traditional stress sources,the thermal stress and the growth-caused stress.The numerical simulations for the structural stress,the thermal stress and the growth-caused stress show that the final sum of these three stresses is close to measured residual stress of the film,proving the accuracy of the theoretical models used.Meanwhile,it is found in simulations that the initial curvature of the substrate had a significant influence on the subsequent yield,further the equilibrium process of these pressures is also analyzed.With Plasma Enhanced Chemical Vapor Deposition（PECVD）,we investigate and improve the stress varying processes and refractive index distribution of SiO₂ film on a 6-inch silicon wafer from both the theoretical calculation and coating process,then find that changing the refractive index of the thin film core layer by the GeH4 flow rate instead of the SiH4 flow rate can improve the film uniformity and reduce the stress.In addition,with the MZI type 2x2 thermo-optical switching device we study the heat conduction characteristics of its switching process,and then optimizes the power consumption and speed of the thermo-optic switch operation.Through the numerical calculation,the beam propagation method（BPM）software simulation,the COMSOL software and experimental tests,we find that the switching power and speed of an MZI type 2x2 thermo-optical switch is dependent the thickness of the upper cladding and heat conductive process.At the same time,the distributions of refractive index and stress on wafer impact the optical loss and polarization dependent loss of devices.The commercialization of PLC components requires high yields in product development and mass production processes,so the stable optical performance of product yield are the important issues.